Counterbalanced windows provide assistance for lifting one or more sashes. For instance, user assistance may be needed to raise some larger window sashes (e.g., some sashes weigh fifty pounds or more), or to assist the elderly, or other users. Counterbalanced windows include individual counterbalance mechanisms and sash-based counterbalance mechanisms.
One example of a balance tube type counterbalance mechanism is provided in Trout, U.S. Pat. No. 4,413,445, entitled “Spring-Stretch-Reducing Window Sash Balance.” In this example, a sash is coupled with a sash cable that extends around a pulley and a travelling pulley. The sash cable is anchored to a sash guide. As with a conventional double hung window, each of the sashes are separately operable, and a user is not able to operate both of the sashes through movement of a single sash. For instance, opening (e.g., raising) the lower sash does not cause opening (e.g., lowering) of the upper sash. For especially large (e.g., tall or wide) windows, such an arrangement may cause additional difficulty for the user as operation of the lower sash does not correspondingly operate the upper sash. Instead, in the case of especially tall windows, a user may have to use a step ladder, or other elevating tool, to reach the upper sash to lower it. Further, it may be difficult to apply leverage to the upper sash at its raised location, for instance from a ladder or while reaching from a standing position and on the balls of one's feet.
Another example of counterbalanced window is shown in Schimmel, U.S. Pat. No. 2,276,881, entitled “Counter-Balanced Window Sash.” In this example, a window includes two sashes that are coupled together using a chain. The chain is wrapped around a pulley. With this mechanism, raising the lower sash lowers the upper sash, and conversely, lowering the upper sash raises the lower sash. This counterbalance arrangement prohibits independent opening and closing of the sashes. Stated another way, as the lower sash is raised to open the window, the upper sash lowers to provide openings at both the top and the bottom of the window frame. Because the movement of one sash results in opposed movement of the other sash, a maximized egress opening (e.g., with the lower sash raised and the upper sash remaining in the elevated and original closed position) is not possible.